This invention relates generally to an apparatus and method for locating a particular portion of an object that is not viewable and in particular to an apparatus and method for locating a portion of an object by placing a marker that is viewable at or near the portion of the object.
In many applications, it is not possible to directly view an object or a portion of an object that needs to be acted on in some manner. For example, to treat a target region, such as a lung tumor, with radiation, it is not possible to be able to view the actual tumor within the patient immediately before the radiation treatment. It is therefore necessary to have some mechanism for permitting the lung tumor to be located accurately so that the radiation treatment can be targeted at the lung tumor while avoiding damage to healthy tissue.
In order to accurately track and target a target region, one or more fiducials may be used. Each fiducial is typically a substance that can be seen when an x-ray of the patient is viewed so that the lung tumor can be effectively located and targeted. Typically, the fiducials may be inserted into the patient during a simple operation. Each fiducial may be, for example, a radio-opaque substance that will be visible during an x-ray of the patient. These typical fiducials permit more accurate locating and targeting of the lung tumor, but there is a limit to the accuracy of targeting that can be achieved with these typical fiducials. In particular, the fiducials are normally placed into the lung tumor, but are not actually anchored to the lung tumor. Therefore, over time, the fiducials may move slightly or a large distance which makes the fiducials useless to locate the lung tumor and requires that new fiducials be inserted into the patient. It may actually be worse if the fiducials only move a small distance since the surgeon may not realize that the fiducials have moved and continue the treatment with bad targeting information (from the misaligned fiducials) that may lead to the radiation being delivered to the wrong location. In fact, the radiation may be delivered less effectively (in a smaller amount) to the lung tumor (which reduces the efficacy of the treatment) and delivered in a greater amount to the healthy tissue surrounding the lung tumor which will damage the healthy tissue and cause undesirable side effects.
To solve this problem, it is desirable to provide fiducials that may be anchored into a target region so that the fiducials are not able to move away from the target region and/or migrate. Thus, it is desirable to provide an anchored fiducial apparatus and it is to this end that the present invention is directed.